Assessment of chemotherapy response in colorectal liver metastases in patients undergoing hepatic resection and the correlation to pathologic residual viable tumor.

BACKGROUND The Response Evaluation Criteria in Solid Tumors (RECIST), which evaluates maximum tumor diameter only, is commonly used to determine response to chemotherapy in patients with colorectal liver metastases. Limitations of RECIST include its inability to assess the changes in tumor enhancement. The aim of this study was to assess the correlation of these criteria as well as the modified RECIST (mRECIST) with pathologic tumor response. A novel semi-automated volumetric assessment of tumor size was also investigated. STUDY DESIGN A review of a 1,948-patient prospective hepatic database to assess response and pathologic criteria was performed. Patients undergoing preoperative chemotherapy before hepatic resection for colorectal liver metastases were reviewed. Radiographic responses according to RECIST and mRECIST were determined. The percentage of viable tumor cells compared with the total tumor area was determined from the pathologic specimens. RESULTS We identified 38 patients with adequate imaging who had undergone anatomic hepatic resection and full pathologic evaluation. The percentages of residual viable tumor in the resected specimens were significantly different across RECIST categories (p = 0.045), but not mRECIST (p = 0.305). For mRECIST, there were improved and significant linear trends for residual viable tumor, necrosis, and necrosis + fibrosis when compared with RECIST (p = 0.056). Neither RECIST nor mRECIST responses were predictive of residual viable tumor burden in regression analyses. A novel semi-automated volumetric assessment of tumor size correlated well with pathologic tumor size. CONCLUSIONS Neither RECIST nor mRECIST were predictive of residual viable burden, although the linear trend for mRECIST and residual necrosis + fibrosis compared favorably with RECIST. Continued evaluation for tumor enhancement and standardization of tumor size remain a critical unmet need in patients with solid organ disease.